1. Field of Invention
This invention relates to digital circuits, specifically to driver circuits for digital data transmission from one physical location to another either on a single integrated circuit or between one or more integrated circuits.
2. Prior Art
Digital input/output circuits used for digital data transmission in integrated circuits in prior art are all dissipative. This means that the electrical energy used to change the potential at the input of the receiving circuits is dissipated as heat each time the data state is changed. In the case of prior art that uses electrical current sensing techniques, all of the energy associated with the current used for signaling is continuously dissipated as heat. Output drivers used in prior art do not recycle charge and make use of energy stored in electric and magnetic fields. This includes all of the input/output standards currently in use such as Low Voltage Transistor-Transistor Logic (LVTTL), Low Voltage Differential Signaling (LVDS), Low Voltage Pseudo Emitter Coupled Logic (LVPECL), High Speed Transceiver Logic (HSTL), Stub Series Terminated Logic (SSTL), Transition Minimized Differential Signaling (TMDS), and so forth.
Power dissipation scales as the square of the voltage; hence, it is desirable to keep the operating voltage as low as possible while still allowing adequate signal to reliably sense the data states on the data lines. This is the reason for using the lowest possible voltage for low-power digital data transmission. Generally the minimum voltage that can be used is determined by the sensitivity of the input or receiving circuitry and the noise level in the environment of the receiving circuitry. Sensing of the data states at the receiving end of the data lines is achieved using any conventional sensing circuits contained in prior art such as a latching sense amplifier. An example of a conventional receiver circuit is included in U.S. Pat. No. 6,426,656 issued 2002 Jul. 30 to William Dally et. al. entitled High Speed, Low-Power Inter-Chip Transmission System. This patent is also a good example of prior art for low-power data transmission in a crossbar switch. In this prior art the amplitude of the differential signals on the data lines is minimized, but the charge required to effect the changes in potentials on the data lines is discharged on every cycle and the energy contained in the electric field of the parasitic capacitances is dissipated as heat energy on every cycle.
Minimizing power dissipation is an important objective for all integrated circuits, but it is especially important for battery-powered applications. Prior art has minimized power dissipation by minimizing the operating voltage, maximizing the sensitivity of the input or receiving circuitry, minimizing noise, and minimizing parasitic capacitances. The electrical energy associated with the currents and/or charge displacements that represent the digital signal outputs in prior art are dissipated as heat during each change of data state.